1. Field of the Invention
The present invention relates generally to underlayments for tile countertops, and more specifically to a self-leveling countertop underlayment, as well as a kit for constructing same.
2. Description of the Related Art
Proper installation of countertop tile first requires that a stable, level underlayment be prepared upon the deck to be tiled. Cabinet decking, over which countertops are usually laid, is normally constructed of plywood, 3/4" exterior grade being the most common type of plywood used. This plywood acts as the substrate for the underlayment to follow.
In the past, underlayments have been constructed in several ways. The most traditional type first requires construction of a metal screed box around the area to be tiled. Metal cap strip is usually used for constructing the screed box. The cap strip has adjustment slots at its points of attachment to the cabinet to permit the screed box to be leveled. Then, a moisture-resistant paper such as roofing felt is laid over the deck's surface. Next, a powdered concrete underlayment compound comprised of sand, cement and lime is mixed with water and packed into the screed box. The underlayment is leveled by repeatedly passing a screed board over its surface and filling low spots with additional mix until the desired surface is achieved.
One of the problems with this method is that the screeding-off process is very time-consuming; extraordinary attention is required to yield a true surface. And, unless an inordinate amount of time is spent in perfecting such an underlayment, any such screeded surface will have some imperfections. Tile setters having skills sufficient to lay tile evenly over such imperfections earn much higher wages than tile setters of only average skill.
More modernly, underlayment is constructed by covering the cabinet's deck with cementitious panels such as are known in the trade and sold as "Wonderboard" and "Durarock." These panels are nailed to the deck. Seams between these panels are covered with tape and then smoothed over with a spreadable underlayment compound, such compound commonly being latex-based. Counter-sunk nail holes in the panels are also filled with this compound. Then, tile is laid thereover.
Cementitious panels make a somewhat more flexible underlayment than concrete and, therefore, are more resistant to cracking. However, with these panels it is very difficult to achieve a truly level surface. Slopes, twists and other imperfections in the substrate are often uncorrectable and tend to be carried through to the overlying tile. Again, higher-skilled, more expensive tile setters must be employed if a quality tile surface is desired.
Thus, it appears that a need exists for a true-surfaced underlayment product that is able to be precisely leveled by lower-paid workers.